Image processing devices and sheet feeding devices

ABSTRACT

An image processing device includes first and second feeding units. The first feeding unit feeds a sheet toward the second feeding unit in a sheet feeding direction via a sheet feeding path. The device further includes an image processing portion. The first feeding unit is in the path upstream of the processing portion and includes a first shaft rotating in the feeding direction. The second feeding unit is in the path downstream of the processing portion, and the first and the second units feed and hold the sheet. The second feeding unit includes a second shaft rotating in the feeding direction. The device includes a first supporting member supporting first and second ends of the first shaft, a second supporting member supporting first and second ends of the second shaft, and a third supporting member supporting one shaft at a predetermined portion which is not either end of either shaft.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims priority from Japanese Patent ApplicationNo. 2007-340874, which was filed on Dec. 28, 2007, the disclosure ofwhich is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to image processing devices comprising asheet feeding device configured to feed sheets, such as documents andrecording mediums, using a plurality of rollers.

2. Description of Related Art

Known scanners, facsimile machines, and copiers, and multifunctiondevices configured to perform the functions of a scanner, a facsimilemachine, and a copier, such as the devices described in U.S. Pat. No.7,080,836 B2 and Japanese Laid-Open Patent Publication Nos. 9-238236 and5-155459, include a sheet feeding device that automatically feedsdocuments stored in a document tray, one by one, to a reading position,or automatically feeds recording mediums held in a sheet cassette to arecording position.

The sheet feeding device includes a plurality of rotating shafts whichare configured to rotate and have a predetermined distance therebetweenin a feeding direction of a sheet. At least one drive roller is mountedto each rotating shaft. When a motor inputs a rotating force to therotating shaft, the drive roller rotates with the rotating shaft. Adriven roller is pressed against a roller surface of the drive roller.Therefore, the driven roller rotates with the drive roller. When theleading end of a sheet reaches a nip position between the drive rollerand the driven roller, the sheet is fed by the drive roller in thefeeding direction.

Referring to FIG. 15, a known roller supporting mechanism is depicted.In the known roller supporting mechanism, first drive rollers 201 aredisposed upstream of second drive rollers 202 in the feeding direction,as indicated by an outline arrow. A rib 207 is disposed at each end of afeeding path 206 in its width direction. First drive rollers 201 aremounted to a rotating shaft 211. The ends of the rotating shaft 211 arerotatably supported by ribs 207. Second drive rollers 202 are mounted torotating shaft 212. The ends of the rotating shaft 212 are rotatablysupported by ribs 207.

When the leading edge of a sheet 208 reaches first drive rollers 201,first drive rollers 201 feed sheet 208 in the feeding direction. Afterthe leading edge of sheet 208 passes first drive roller 201 and reachessecond drive rollers 202, second drive rollers 202 feed sheet 208. Afterthe leading edge of sheet 208 reaches second drive rollers 202 andbefore the trailing end of sheet 208 passes over first drive rollers201, both first drive rollers 201 and second drive rollers 202 feedsheet 208. When the circumferential velocity of first drive rollers 201is greater than the circumferential velocity of second drive rollers202, sheet 208 flexes between first drive rollers 201 and second driverollers 202, and may be damaged. Therefore, the circumferential velocityof second drive rollers 202 disposed on the downstream side in thefeeding direction is adjusted to be slightly greater than thecircumferential velocity of first drive rollers 201. Accordingly, afirst feeding force with which first drive rollers 201 feed sheet 208 isgreater than a second feeding force with which second drive rollers 202feed sheet 208, such that sheet 208 is held under tension between firstdrive rollers 201 and second drive rollers 202.

The known sheet feeding device only supports rotating shafts 211 and 212at their ends. Consequently, the difference between the circumferentialvelocity of first drive rollers 201 and the circumferential velocity ofsecond drive rollers 202 causes a tensile force. The tensile force pullssheet 208 while generating a frictional force which draws rotatingshafts 211 and 212 closer to each other. The frictional force causesrotating shafts 211 and 212 to flex toward each other, as indicated bydotted lines in FIG. 15. After the trailing end of sheet 208 passes overfirst drive rollers 201, flexed rotating shafts 211 and 212 return totheir original positions. At this time, sheet 208 moves in the feedingdirection by an amount corresponding to an amount that flexed rotatingshaft 212 of second drive rollers 202 moves from its original positionwhen shaft 212 flexes. As a result, a feeding failure occurs and placesthe document out of position with respect to the feeding direction. Whena feeding failure occurs during the process of reading an image recordedon sheet 208 or during the process of recording an image on sheet 208,read image data or recorded sheet 208 will have streaks. Thus, theaccuracy of reading an image or recording an image is reduced.

When sheet 208 is stopped intermittently while being fed by first driverollers 201 and second drive rollers 202, a feeding failure occurs dueto various factors, such as non-uniform friction forces applied to firstdrive rollers 201 and second drive rollers 202 when the sheet feeding istemporarily stopped and resumed, non-uniform amounts of flexing ofrotating shafts 211 and 212 at the timing of stopping and resuming ofthe sheet feeding, or non-uniform flexing amounts of an elastic member,such as rubber, at the time of stopping and resuming of the sheetfeeding if an elastic member is disposed or applied on a surface ofdrive rollers 201 and 202. Such feeding failure causes streaks in theread image data or in an image recorded on a sheet 208. Thus, theaccuracy of reading an image or recording an image is reduced.

The above problems occur on small-diameter rotating shafts used toreduce the weight of the sheet feeding devices. The problems also occuron image reading devices having auto document feeders (ADF) that feedlarge-sized documents, such as A3 size, or on inkjet-type imagerecording apparatuses configured to record an image on large-sizerecording sheets, such as size A3, because the amount of flexing ofrotating shafts 211 and 212 increases in these devices.

SUMMARY OF THE INVENTION

Therefore, a need has arisen for image processing devices and sheetfeeding devices which overcome these and other shortcomings of therelated art. A technical advantage of the present invention is thatfeeding failures caused by differences in circumferential velocity ofthe rollers are reduced, which increases the quality of imageprocessing.

According to an embodiment of the present invention, an image processingdevice comprises a first feeding unit, a second feeding unit, and animage processing portion. The first feeding unit is coupled to thesecond feeding unit via a sheet feeding path, and is configured to feeda sheet toward the second feeding unit in a sheet feeding direction viathe sheet feeding path. The first feeding unit is disposed in the sheetfeeding path upstream of the image processing portion in the sheetfeeding direction, and the first feeding unit comprises a first shaftconfigured to rotate in the sheet feeding direction, a first driveroller coupled to the first shaft, and a first pressing memberconfigured to apply a force to the first drive roller. The secondfeeding unit is disposed in the sheet feeding path downstream of theimage processing portion in the sheet feeding direction, and the firstfeeding unit and the second feeding unit are configured to feed and holdthe sheet simultaneously. The second feeding unit comprises a secondshaft configured to rotate in the feeding direction, a second driveroller coupled to the second shaft, and a second pressing memberconfigured to apply a force to the second drive roller. The imageprocessing device further comprises a first supporting member whichrotatably supports each of a first end of the first shaft and a secondend of the first shaft, a second supporting member which rotatablysupports each of a first end of the second shaft and a second end of thesecond shaft, and a third supporting member which rotatably supports atleast one of the first shaft and the second shaft, at at least onepredetermined portion which is different than each end of the at leastone of the first shaft and the second shaft.

According to another embodiment of the present invention, a sheetfeeding device comprises a first feeding unit, a second feeding unit anda reference member. The first feeding unit is coupled to the secondfeeding unit via a sheet feeding path, and is configured to feed a sheettoward the second feeding unit in a sheet feeding direction via thesheet feeding path. The reference member comprises a reference surfacewhich the sheet contacts during image processing. The first feeding unitis disposed in the sheet feeding path upstream of the reference memberin the sheet feeding direction, and the first feeding unit comprises afirst shaft configured to rotate in the sheet feeding direction, a firstdrive roller coupled to the first shaft, and a first pressing memberconfigured to apply a force to the first drive roller. The secondfeeding unit is disposed in the sheet feeding path downstream of thereference member in the sheet feeding direction, and the first feedingunit and the second feeding unit are configured to feed and hold thesheet simultaneously. The second feeding unit comprises a second shaftconfigured to rotate in the feeding direction, a second drive rollercoupled to the second shaft, and a second pressing member configured toapply a force to the second drive roller. The image feeding devicefurther comprises a first supporting member which rotatably supportseach of a first end of the first shaft and a second end of the firstshaft, a second supporting member which rotatably supports each of afirst end of the second shaft and a second end of the second shaft, anda third supporting member which rotatably supports at least one of thefirst shaft and the second shaft, at at least one predetermined portionwhich is different than each end of the at least one of the first shaftand the second shaft.

Other objects, features, and advantages of embodiments of the presentinvention will be apparent to persons of ordinary skill in the art fromthe following description of preferred embodiments with reference to theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, the needssatisfied thereby, and the objects, features, and advantages thereof,reference now is made to the following description taken in connectionwith the accompanying drawings.

FIG. 1 is a perspective view of an auto document feeder (ADF), accordingto an embodiment of the invention.

FIG. 2 is a cross-sectional view of the ADF of FIG. 1, taken along theline II-II of FIG. 1.

FIG. 3 is a plan view of the ADF with an ADF cover removed.

FIG. 4 is a plan view of the ADF and an upper guide with the ADF coverremoved.

FIG. 5 is a perspective view of the ADF with the ADF cover and an outputunit removed.

FIG. 6A is an enlarged view of a portion VIA of FIG. 5.

FIG. 6B is an enlarged view of a portion VIB of FIG. 5.

FIG. 6C is an enlarged view of a portion VIC of FIG. 5.

FIG. 6D is an enlarged view of a portion VID of FIG. 5.

FIG. 7 is a perspective view of the output unit.

FIG. 8A is a top view of a bearing of the ADF.

FIG. 8B is a front view of the bearing of the ADF.

FIG. 8C is a rear view of the bearing of the ADF.

FIG. 8D is a side view of the bearing of the ADF.

FIG. 8E is a cross-sectional view of the bearing, taken along lineVIIIE-VIIIE of FIG. 8A.

FIG. 9 is a schematic showing tensile forces applied to a document at aninstance of document feeding operation.

FIG. 10 is a schematic showing tensile forces applied to the document atanother instance of document feeding operation

FIG. 11 is a schematic showing tensile forces applied to the document atyet another instance of document feeding operation

FIG. 12 is a schematic showing tensile forces applied to the document ata further instance of document feeding operation

FIG. 13 is a schematic showing tensile forces applied to the document atyet a further instance of document feeding operation.

FIG. 14 is a schematic of a third supporting member according to anembodiment of the invention.

FIG. 15 is a schematic showing a known roller supporting mechanism.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Embodiments of the present invention and their features and technicaladvantages may be understood by referring to FIGS. 1-14, like referencenumerals being used for like corresponding portions in the variousdrawings.

An automatic document feeder (ADF) 10 may be configured to feed sheets,e.g., documents and recording mediums, along a feeding path 16.Referring to FIG. 1, ADF 10 may comprise a document tray 12 for loadingdocuments and an output tray 14 for outputting documents. Referring toFIG. 2, an interior of ADF 10 may comprise feeding path 16. ADF 10automatically and continuously may feed documents in a feeding directionfrom document tray 12 to output tray 14 via feeding path 16. ADF 10 maybe disposed on an image processing device 20, e.g., an image readingdevice.

Image processing device 20 may comprise a contact glass 22 disposed atan upper portion of image processing device 20 and an image processingportion 24, e.g., an image sensor. Image processing portion 24 maycomprise a contact image sensor (CIS) or a charge coupled device (CCD).The CIS or the CCD may be disposed below contact glass 22. ADF 10 maycover the upper surface of image processing device 20. When a documentfed by ADF 10 passes over an image reading position on contact glass 22,image processing portion 24 may read an image on the surface of thedocument. Image reading device 20 may be coupled to ADF 10. ADF 10 maybe configured to work with any image processing device, e.g., an imagerecording device configured to record an image on recording mediums,such as paper sheets, by applying an image recording agent, such astoner or ink, to the recording mediums. ADF 10 also may be configured towork with sheet feeding devices which feed recording mediums to an imagerecording position in the image recording devices.

Document tray 12 and output tray 14 may be stacked generally in avertical direction. More specifically, document tray 12 may be disposedabove output tray 14. Document tray 12 may comprise an upper guide 34and an extension tray 38. Output tray 14 may be formed in a recessingupper surface of ADF 10. Output tray 14 may be disposed above or belowdocument tray 12.

Referring to FIG. 2, feeding path 16 may have substantially a “U” shapewhen viewed in a vertical cross section. Feeding path 16 may connectdocument tray 12 to output tray 14. Feeding path 16 may comprise anupper feeding portion 16A, a curved feeding portion 16B, and a lowerfeeding portion 16C. As shown in FIG. 2, upper feeding portion 16A mayextend leftward from document tray 12, curved feeding portion 16B maycurve downward from upper feeding portion 16A, and lower feeding portion16C may extend rightward from curved feeding portion 16B toward outputtray 14. In another embodiment, feeding path 16 may be substantially astraight line.

A case of ADF 10 may comprise a main frame 30, an ADF cover 32, upperguide 34, and a lower guide 36. The case of ADF 10 may comprisesynthetic resin, e.g., acrylonitrile butadiene styrene (ABS),polypropylene, or polyacetal, and may be formed by injection molding.ADF cover 32, upper guide 34 and lower guide 36 may be attached to mainframe 30.

Upper guide 34 and lower guide 36 may be disposed in a stacked manner inthe vertical direction. Lower guide 36 may be attached to main frame 30to define lower feeding portion 16C. Lower feeding portion 16C maycomprise a passage formed between an upper surface of main frame 30 anda lower surface of lower guide 36 allowing a document to passtherethrough. Lower guide 36 may function as a guide surface of lowerfeeding portion 16C. Upper guide 34 may be attached to an upper portionof lower guide 36. As shown in FIG. 2, ADF cover 32 may be pivotallysupported by main frame 30 about a left end portion thereof, and may beconfigured to pivotally open and close. When ADF cover 32 is closed, ADFcover 32 covers a portion of ADF 10 from the left end portion of mainframe 30 to a portion of upper guide 34. When ADF cover 32 is closed, arear surface of ADF cover 32 and an upper surface of upper guide 34 maydefine upper feeding portion 16A with a passage allowing a document topass therethrough. As such, upper guide 34 may function as a guidesurface of upper feeding portion 16A.

A portion of upper guide 34 may extend outward from upper feedingportion 16A. Extension tray 38 may be attached to an upstream end ofupper guide 34 in the feeding direction. Extension tray 38 may besupported by upper guide 34, and may fold over upper guide 34.

A feeding roller 62 may be disposed on the downstream side of upperguide 34 and the upstream side of lower guide 36 in the feedingdirection. Feeding roller 62 may be rotatably supported by main frame30. Feeding roller 62 and main frame 30 may define curved feedingportion 16B with a passage allowing a document to pass therethrough.

A stack of documents may be loaded on document tray 12, and the leadingends of the documents may be inserted into a chute 44. Chute 44 may bedisposed on the most upstream side of upper feeding portion 16A in thefeeding direction. Surfaces of documents containing images to be readmay face upward on document tray 12. When ADF 10 feeds documents fromdocument tray 12 through curved feeding portion 16B of feeding path 16,the documents may be turned upside down with the surface of thedocuments containing images to be read facing down. Then, the documentsmay be fed to lower feeding portion 16C, and may be outputted to andstacked on output tray 14 with the surfaces of the documents containingimages that were read facing down.

Referring to FIG. 2, lower guide 36 may comprise a reference member 46which presses documents against contact glass 22 when the documents arefed through lower feeding portion 16C. Reference member 46 may bedisposed at a position corresponding to an image reading position atwhich image processing portion 24 reads a surface of a documentcontaining images to be read. More specifically, reference member 46 maybe attached to a lower surface of lower guide 36. Reference member 46may be movably supported in the vertically direction. A spring 48 may bedisposed between the lower surface of lower guide 36 and referencemember 46, such that reference member 46 is elastically urged downwardby spring 48. Thus, reference member 46 may extend toward lower feedingportion 16C.

When the leading end of a document reaches reference member 46, theleading end may enter a space between reference member 46 and contactglass 22. At this time, a reference surface 49 of reference member 46,e.g., a lower surface, may contact a lower surface of a document.Therefore, even when a wrinkled document is fed to reference member 46,the document may be held between the lower surface of reference member46 and contact glass 22, such that the wrinkled document is flattened.

Referring to FIG. 1, document tray 12 may comprise a pair of documentguides 13 spaced apart in a depth direction of ADF 10. Document guides13 may be slidable in the depth direction of ADF 10. Document guides 13may align the position of documents, which are loaded onto document tray12, in their lateral direction. When one of document guides 13 moves inone direction, the other document guide 13 may move in the oppositedirection by an interlocking mechanism. Therefore, when documents areloaded onto document tray 12, document guides 13 may align the center ofthe documents in their lateral direction with the center of documenttray 12 in its lateral direction.

A feeding mechanism configured to feed documents may be disposed infeeding path 16. More specifically, the feeding mechanism may comprise asupply unit 50, a first feeding unit 60, and a second feeding unit 70.Supply unit 50, first feeding unit 60 and second feeding unit 70 maysequentially be arranged in the feeding direction.

Referring to FIGS. 2 and 3, supply unit 50 may be disposed in upperfeeding portion 16A. Specifically, supply unit 50 may be disposed atchute 44 located on the most upstream side of upper feeding portion 16Ain the feeding direction. Supply unit 50 may comprise a pickup roller52, a separation roller 54 and a shaft 56. Shaft 56 may be rotatablysupported at each of its ends by main frame 30. Separation roller 54 maybe fixedly mounted at a middle portion of shaft 56 in its axialdirection. A motor (not shown) may transmit a rotational force to shaft56 in a predetermined direction, e.g., a clockwise direction in FIG. 2.When shaft 56 rotates, separation roller 54 may rotate in the samedirection as shaft 56. In this embodiment, separation roller 54 mayrotate at a circumferential velocity V1.

An arm 58 may be rotatably disposed on shaft 56. Arm 58 may comprise twobearings (not shown). Each bearing may be supported by shaft 56 at anend of separation roller 54 in an axial direction. Arm 58 may extendfrom shaft 56 toward the upstream end of the feeding direction. Pickuprollers 52 may be rotatably disposed at an upstream end of arm 58. Themotor may transmit a rotational force to arm 58 to rotate arm 58 onshaft 56.

Transmission gears (not shown) may be assembled with arm 58. Thetransmission gears may transmit a rotational force from shaft 56 topickup rollers 52. When shaft 56 rotates, both separation roller 54 andpickup rollers 52 may rotate in the same direction as shaft 56. Pickuprollers 52 and separation roller 54 may have the same diameter and mayrotate at the same circumferential velocity.

A separation pad 57 may be disposed opposite separation roller 54.Separation pad 57 may be in contact with a roller surface of separationroller 54 to separate documents, one by one, by friction. When shaft 56rotates, documents may be separated, one by one, by separation pad 57,and then may be fed to feeding path 16.

Referring to FIG. 2, feeding unit 60 may be disposed in curved feedingportion 16B. Feeding unit 60 may be disposed in feeding path 16 upstreamof reference member 46 in the feeding direction. Feeding unit 60 maycomprise a first drive roller 62, first pressing rollers 63 and 64, anda first shaft 66. First shaft 66 may comprise steel, e.g., stainlesssteel, aluminum alloy, or synthetic resin. Referring to FIGS. 4 and 5,first shaft 66 may be rotatably supported at its ends by firstsupporting members, e.g., supporting mechanisms 80 and 90, at main frame30. First shaft 66 also may be supported at portions other than its endsin the direction along feeding path 16 by third supporting members,e.g., supporting mechanisms 100 and 110.

Referring to FIGS. 4 and 5, feeding roller 62 may be fixedly mounted toa middle portion of first shaft 66. A roller surface of feeding roller62 may comprise an elastic member, e.g., a sponge or a rubber, toimprove a tackiness of the roller surface to a document when feedingroller 62 contacts a document. The motor (not shown) may transmit arotational force to first shaft 66 in a rotational direction, e.g., acounterclockwise direction in FIG. 2, to feed a document in the feedingdirection. When shaft 66 rotates, feeding roller 62 may rotate in thesame rotational direction as shaft 66. In this embodiment, feedingroller 62 may rotate at a second circumferential velocity V2, which maybe greater than the circumferential velocity V1 of separation roller 54.

Referring to FIG. 2, pinch roller 63 may be disposed opposite and abovefeeding roller 62. Pinch roller 63 may press against the roller surfaceof feeding roller 62. Pinch roller 63 may be rotatably supported by arib disposed at an underside of ADF cover 32. A shaft of pinch roller 63may be elastically urged by an elastic member, e.g., a spring. When ADFcover 32 is open, pinch roller 63 may become separated from feedingroller 62. When ADF cover 32 is closed, pinch roller 63 may pressagainst the roller surface of feeding roller 62, as shown in FIG. 2.

Pinch roller 64 may be disposed opposite and below feeding roller 62.Pinch roller 64 may be disposed downstream of pinch roller 63 in thefeeding direction. Pinch roller 64 may be rotatably supported by a ribdisposed at an underside of main frame 30. A shaft of pinch roller 64may be elastically urged by an elastic member, e.g., a spring. Thus,pinch roller 64 may press against the roller surface of feeding roller62.

When feeding roller 62 rotates with pinch rollers 63 and 64 pressingagainst feeding roller 62, pinch rollers 63 and 64 also may rotate. Whenthe leading end of a document fed in the feeding direction by supplyunit 50 reaches a nip position between feeding roller 62 and pinchroller 63 or a nip position between feeding roller 62 and pinch roller64, the document may be fed by the rotational force of feeding roller 62in the feeding direction while being held between feeding roller 62 andpinch roller 63 or between feeding roller 62 and pinch roller 64. Thedocument simultaneously may be fed by separation roller 54 and feedingroller 62. As described above, the circumferential velocity V2 offeeding roller 62 may be greater than the circumferential velocity VI ofseparation roller 54. Therefore, when a document simultaneously is fedby separation roller 54 and feeding roller 62, a tensile force may beapplied to the document in the direction along the feeding direction.

In an embodiment, pinch rollers 63 and 64 may press against feedingroller 62 at positions above and below feeding roller 62. Nevertheless,the number and the positions of rollers 62, 63, and 64 may vary. Forexample, a plurality of feeding rollers 62 may be concentricallydisposed along the depth direction of ADF 10. A member, such asseparation pad 57, instead of a roller shape member, e.g., pinch rollers63 and 64, may be disposed in contact with feeding roller 62.

Referring to FIGS. 5-6D, first shaft 66 may be supported at its ends bysupporting mechanisms 80 and 90. First shaft 66 also may be supported atportions adjacent to the edge of feeding roller 62 in its axialdirection by supporting mechanisms 100 and 110. More specifically,supporting mechanisms 80 and 90 may support a front end 67 and a rearend 68, respectively, of shaft 66. Supporting mechanisms 100 and 110 maysupport first shaft 66 at positions adjacent to a front end and a rearend, respectively, of feeding roller 62 in its axial direction.

Referring to FIG. 6A, supporting mechanism 80 may comprise a supportinggroove 81 and a bush 82. Supporting groove 81 may be formed on a rib 86extending from main frame 30. More specifically, supporting groove 81may be formed by removing a portion of rib 86 from its upper side towardits lower side. Bush 82 may be coupled to supporting groove 81. Bush 82may comprise a synthetic resin, such as polyacetal (POM), which hashigher slidability than rib 86. Bush 82 may comprise a cylindrical,tubular body 83 and a flange 84. Front end 67 of shaft 66 may have agroove 87 formed on a periphery thereof. When front end 67 is insertedinto the hole of tubular body 83, a hook 85 disposed on bush 82 mayengage groove 87. Thus, front end 67 may be rotatably coupled to bush82, and tubular body 83 may be coupled to supporting groove 81. As such,front end 67 of first shaft 66 may be rotatably supported by supportingmechanism 80.

Referring to FIG. 6B, supporting mechanism 90 may comprise a supportinggroove 91 formed on a rib 96, and a bush 92 coupled to supporting groove91. Bush 92 may comprise a cylindrical, tubular body 93 and a flange 94.Tubular body 93 may be coupled to supporting groove 91. Rear end 68 ofshaft 66 may be inserted into the hole of tubular body 93. Thus, rearend 68 of shaft 66 may be rotatably supported by supporting mechanism90. Rib 96 may comprise a conductive metal, and bush 92 may comprise aconductive resin. Therefore, static electricity generated on shaft 66may dissipate from the case of ADF 10 via bush 92 and rib 96.

Referring to FIG. 6C, supporting mechanism 100 may comprise a supportinggroove 101 and a bush 102. Supporting groove 101 may be formed on a rib106 which extends from main frame 30. More specifically, supportinggroove 101 may be formed by removing a portion of rib 106 from its upperside toward its lower side. Bush 102 may be coupled to supporting groove101. Bush 102 may comprise a synthetic resin, such as polyacetal (POM),which has higher slidability than rib 106. Bush 102 may comprise acylindrical, tubular body 103 and a flange 104. First shaft 66 may beinserted into the hole of tubular body 103. Bush 102 may be coupled tofirst shaft 66 at a position adjacent to the frond end face of feedingroller 62 in its axial direction. When bush 102 is coupled to firstshaft 66, tubular body 103 may be coupled to supporting groove 101.Thus, first shaft 66 may be rotatably supported by supporting mechanism100. Flange 104 may function as a stopper to prevent bush 102 fromseparating from first shaft 66.

Referring to FIG. 6D, supporting mechanism 110 may comprise a supportinggroove 111 formed on a rib 116, and a bush 112 coupled to supportinggroove 111. Supporting mechanism 110 may be substantially similar tosupporting mechanism 100.

Referring to FIG. 2, output unit 70 may be disposed in lower feedingportion 16C. An output chute 45 may be disposed at the most downstreamside of feeding path 16 in the feeding direction. Output unit 70 may bedisposed in feeding path 16 downstream of reference member 46 in thefeeding direction. Output unit 70 may comprise a second drive roller,e.g., an output roller 72, a second pressing member, e.g., a pinchroller 74, and a second shaft, e.g., a shaft 76. Shaft 76 may comprisesteel, e.g., stainless steel, aluminum alloy, or synthetic resin.Referring to FIGS. 4 and 5, shaft 76 may be rotatably supported at itsends by second supporting members, e.g., supporting mechanism 120 and121, located at lower guide 36. Shaft 76 also may be supported atportions other than its ends by third supporting members, e.g.,supporting mechanism 140 and 141

Referring to FIGS. 4 and 5, output rollers 72A and 72B may beconcentrically mounted to shaft 76. Output rollers 72A and 72B may bedisposed on the front side and rear side, respectively, of ADF 10.Roller surfaces of output rollers 72A and 72B may comprise an elasticmember, e.g., a sponge or a rubber, to improve a tackiness of the rollersurfaces to a document when feed output rollers 72A and 72B contact adocument. There may be a predetermined distance between output rollers72A and 72B. The motor may transmit a rotational force to shaft 76 in arotational direction, e.g., a counterclockwise direction in FIG. 2, tofeed a document in the feeding direction. When shaft 76 rotates, outputrollers 72A and 72B may rotate in the same rotational direction as shaft76. In an embodiment, output rollers 72A and 72B may rotate at a thirdcircumferential velocity V3, which may be greater than thecircumferential velocity V2 of feeding roller 62.

Referring to FIG. 2, pinch roller 74 may be disposed below output roller72. Pinch rollers 74A and 74B may be disposed below output rollers 72Aand 72B, respectively. Output roller 72A and 72B may contact the rollersurfaces of output rollers 72A and 72B, respectively. Each pinch roller74A and 74B may be rotatably supported by main frame 30. Shafts of pinchrollers 74A and 74B may be elastically urged by an urging member, e.g.,a spring. Thus, pinch rollers 74A and 74B may press against the rollersurfaces of output rollers 72A and 72B.

When output roller 72 rotates with pinch roller 74 pressed againstoutput roller 72, pinch roller 74 may rotate. When the leading end ofthe document fed by feeding roller 62 reaches a nip position betweenoutput roller 72 and pinch roller 74, the document may be fed by therotational force of output roller 72 in the feeding direction whilebeing held by output roller 72 and pinch roller 74. The document may besimultaneously fed by feeding roller 62 and output roller 72. Asdescribed above, the circumferential velocity V3 of output roller 72 maybe greater than the circumferential velocity V2 of feeding roller 62.Therefore, when a document is fed both by feeding roller 62 and outputroller 72, a tensile force may be applied to the document in thedirection along the feeding direction.

In an embodiment, two output rollers 72A and 72B may be fixed to shaft76, however, the number and the positions of output rollers 72A and 72Bmay vary.

Referring to FIGS. 4, 5, and 7, a front end 77 and a rear end 78 ofshaft 76 may be supported by supporting mechanisms 120 and 121. Portionsof shaft 76 adjacent to a front end of output roller 72A and a rear endof output roller 72B may be supported by supporting mechanisms 140 and141, respectively. Supporting mechanism 121 may be substantially similarto supporting mechanism 90.

Supporting mechanism 120 may comprise a shaft hole 123, as shown in FIG.5, and a bush 124, as shown in FIG. 7. Shaft hole 123 may be formed on arib 125 which extends from lower guide 36. Bush 124 may be coupled toshaft hole 123. Bush 124 may comprise a synthetic resin, such aspolyacetal (POM), which has higher slidability than rib 125. Referringto FIG. 7, bush 124 may comprise a cylindrical, tubular body 126, hooks128, elastically-deformable engagement portions 129, and a flange 127.

End 77 of shaft 76A may have a groove 131 formed on its periphery. Whenend 77 is inserted into the hole of tubular body 126, hooks 128 mayengage groove 131. Thus, bush 124 may be rotatably coupled to end 77.Tubular body 126 may be inserted into shaft hole 123. When tubular body126 is being inserted into shaft hole 123, engagement portions 129 maybe pressed by the inner peripheral surface of shaft hole 123 and mayflex toward an outer peripheral surface of tubular body 126. Whentubular body 126 is further inserted into shaft hole 123 at a positionwhere flange 127 contacts rib 125, flexed engagement portions 129 mayreturn to their original positions to engage the periphery of shaft hole123. Thus, bush 124 may be coupled to rib 125. End 77 may be rotatablysupported by supporting mechanism 120.

Referring to FIGS. 4 and 5, supporting mechanism 140 may comprise abearing 150 and an attachment portion 160. Bearing 150 may be attachedto attachment portion 160. Supporting mechanism 141 may be substantiallysimilar to supporting mechanism 140.

Attachment portion 160 may be formed on the upper surface of lower guide36. Attachment portion 160 may comprise a recess 163 having arectangular shape, a boss 162 to which a screw may be fastened, and twohooks 164 configured to secure bearing 150. As shown in FIG. 7, recess163 may accommodate a fixing portion 151 of bearing 150. Boss 162 andhooks 164 may extend from the bottom surface of recess 163.

Referring to FIGS. 8A-8E, bearing 150 may comprise fixing portion 151which may be attached to attachment portion 160 and a contact portion,e.g., a supporting portion 153, which contacts the periphery of shaft 76to rotatably support shaft 76. Bearing 150 may comprise a syntheticresin, such as polyacetal (POM), that has higher slidability than lowerguide 36.

Supporting portion 153 may have a tubular shape and a hole 157 formedtherethrough, and a shaft 76 may be inserted through hole 157. Whenshaft 76 is inserted into hole 157, an inner surface of hole 157 mayslide against an outer peripheral surface of shaft 76. With shaft 76inserted into hole 157, fixing portion 151 may be attached to attachmentportion 160. Fixing portion 151 may have a generally rectangular shape.When fixing portion 151 is mounted to attachment portion 160, fixingportion 151 may extend from supporting portion 153 in feeding path 16along feeding path 16 toward the upstream side of the feeding direction.

Each side face of fixing portion 151 may comprise a protrusion 155. Eachprotrusion 155 may extend along feeding path 16. Hooks 164 of attachmentportion 160 may engage with respective protrusions 155. Protrusions 155may increase the rigidity of fixing portion 151 along the feedingdirection. Protrusions 155 may be disposed at positions corresponding tothe positions of hooks 164. Fixing portion 151 may have a hole 154formed in a middle portion thereof. When fixing portion 151 isaccommodated in attachment portion 160, hole 154 may be positioned overboss 162 and hooks 164 may engage respective protrusions 155. Thus,fixing portion 151 may be tentatively fixed to attachment portion 160while a screw is fastened to boss 162 to permanently secure fixingportion 151 to attachment portion 160.

Referring to FIG. 4, supporting mechanism 140 may be disposed at theupstream end of shaft 76 in the feeding direction. More specifically,with fixing portion 151 fixed to attachment portion 160, shaft 76 may besupported by supporting portion 153 at a position downstream of fixingportion 151 in the feeding direction.

Ends 77 and 78 of shaft 76 may be supported by supporting mechanisms 120and 121. Portions of shaft 76 adjacent to output roller 72 may besupported by supporting mechanisms 140 and 141.

Referring to FIG. 9, a document loaded on document tray 12 may be fed inthe feeding direction by separation roller 54. When the leading end ofthe document, shown by dotted lines, reaches a point P1 betweenseparation roller 54 and pinch roller 63, a tensile force may not beapplied in the feeding direction to the document, however, a compressionforce may be applied to the document by rollers, e.g., separation roller54, feeding roller 62, and output roller 72, in the vertical direction.

Referring to FIG. 10, when the leading end of the document reaches apoint P2 between pinch rollers 63 and 64, the document may be fed whilebeing held between separation roller 54 and separation pad 57 andbetween feeding roller 62 and pinch roller 63. Thus, the document may befed by both separation roller 54 and feeding roller 62. Thecircumferential velocity V2 of feeding roller 62 may be greater than thecircumferential velocity V1 of separation roller 54. Therefore, thedocument may receive a tensile force and may be pulled along the feedingdirection. A frictional force M1 in the feeding direction may begenerated between the document and separation roller 54 at the nipposition between separation roller 54 and separation pad 57. A frictionforce M2 in a direction opposite to the feeding direction may begenerated between the document and feeding roller 62 at the nip positionbetween feeding roller 62 and pinch roller 63. Frictional forces M1 andM2 may act in opposite directions to draw shaft 56 of separation roller54 and shaft 66 of feeding roller 66 closer to each other.

Referring to FIG. 11, when the leading end of the document reaches apoint P3 between pinch roller 64 and output roller 72, the document maybe fed while being held between separation roller 54 and separation pad57, between feeding roller 62 and pinch roller 63, and between feedingroller 62 and pinch roller 64. Thus, the document may be fed by supplyunit 50 and feeding unit 60. At this time, a frictional force M3 in thefeeding direction may be generated between the document and feedingroller 62 at the nip position between feeding roller 62 and pinch roller63. A magnitude of frictional force M3 may be the same as a magnitude offrictional force M2, and a direction of frictional force M3 may beopposite the direction of frictional force M2. Therefore, frictionalforces M2 and M3 may cancel each other out at the nip position betweenfeeding roller 62 and pinch roller 63.

Further, a frictional force M4 in the direction opposite to the feedingdirection may be generated between the document and feeding roller 62 atthe nip position between feeding roller 62 and pinch roller 64. In anembodiment, only frictional force M4 may be generated at the nipposition between feeding roller 62 and pinch roller 64 until thedocument held by output unit 70 passes the reading position of imageprocessing portion 24. Shaft 66 may be supported at each end thereof bysupporting mechanisms 80 and 90 and at two portions of shaft 66 bysupporting mechanisms 100 and 110. Therefore, even when frictional forceM4 is generated, shaft 66 may not flex. Consequently, even when feedingof the document is temporarily stopped during document feeding, aquality of image reading may not be reduced.

Referring to FIG. 12, when the leading end of the document reachesoutput tray 14, the document may be fed while being held betweenseparation roller 54 and separation pad 57, between feeding roller 62and pinch roller 63, between feeding roller 62 and pinch roller 64, andbetween output roller 72 and pinch roller 74. Thus, the document may befed by supply unit 50, feeding unit 60, and output unit 70. At thistime, a frictional force M5 in the feeding direction may be generatedbetween the document and feeding roller 62 at the nip position betweenfeeding roller 62 and pinch roller 64. Frictional force M5 may have thesame magnitude as frictional force M4, and a direction of frictionalforce M5 may be opposite to the direction of frictional force M4.Therefore, frictional forces M4 and M5 may cancel each other out at thenip position between feeding roller 62 and pinch roller 64.

A frictional force M6 in the direction opposite to the feeding directionmay be generated between the document and output roller 72 at the nipposition between output roller 72 and pinch roller 74. As shown in FIG.13, frictional force M6 constantly may be applied in the same directionat the nip position between output roller 72 and pinch roller 74 untilthe trailing end of the document passes through the nip position betweenfeeding roller 62 and pinch roller 64. Shaft 76 may be supported at itsends by supporting mechanisms 120 and 121 and at two portions thereof bysupporting mechanisms 140 and 141. Therefore, even when frictional forceM6 is generated, shaft 76 may not flex. Consequently, even when thetrailing end of the document passes through the nip position betweenfeeding roller 62 and pinch roller 64, a quality of image reading maynot be reduced.

As described above, each supporting mechanism 140 and 141 may comprisebearing 150 and attachment portion 160. Fixing portion 151 of bearing150 may extend along feeding path 16. Fixing portion 151 may be attachedto attachment portion 160. Bearing 150 securely may be mounted toattachment portion 160. Therefore, external forces applied to shaft 76may not flex shaft 76 because fixing portion 151 securely is mounted toattachment portion 160. Thus, flexing of shaft 76 reliably may bereduced.

Referring to FIG. 14, in another embodiment of the present invention, arestriction rib 170 may replace mechanisms 140 and 141. Restriction rib170 may be disposed upstream of shaft 76 in the feeding direction, asindicated by an outline arrow in FIG. 14. Restriction rib 170 maysupport shaft 76 in the direction along feeding path 16. Similarly,another restriction rib 170 may replace supporting mechanisms 100 and110 to support shaft 66. Restriction ribs 170 may reduce flexing ofshaft 66 and 76 along feeding path 16.

While the invention has been described in connection with variousexemplary structures and illustrative embodiments, it will be understoodby those skilled in the art that other variations and modifications ofthe structures and embodiments described above may be made withoutdeparting from the scope of the invention. Other structures andembodiments will be apparent to those skilled in the art from aconsideration of the specification or practice of the inventiondisclosed herein. It is intended that the specification and thedescribed examples are illustrative with the true scope of the inventionbeing defined by the following claims.

What is claimed is:
 1. An image processing device comprising: aconveying mechanism configured to convey a sheet in a conveyancedirection along a conveyance path; and a sensor disposed in theconveyance path; the conveying mechanism comprising: a first shaftdisposed downstream of the sensor in the conveyance direction and havinga first-shaft first supported portion, a first-shaft second supportedportion and a first-shaft third supported portion positioned between thefirst-shaft first supported portion and the first-shaft second supportedportion; a second shaft disposed upstream of the sensor in theconveyance direction and having a second-shaft first supported portionand a second-shaft second supported portion; a first-shaft firstsupporting portion configured to support the first-shaft first supportedportion and having a bearing configured to receive the first-shaft firstsupported portion; a first-shaft second supporting portion configured tosupport the first-shaft second supported portion and having a bearingconfigured to receive the first-shaft second supported portion; afirst-shaft third supporting portion configured to support thefirst-shaft third supported portion at an upstream side of theconveyance direction and having a bearing configured to receive thefirst-shaft third supported portion; a second-shaft first supportingportion configured to support the second-shaft first supported portion;and a second-shaft second supporting portion configured to support thesecond-shaft second supported portion; wherein a velocity at which thefirst shaft is rotated is greater than a velocity at which the secondshaft is rotated.
 2. The image processing device of claim 1, wherein theconveying mechanism comprises a second-shaft third supporting portionconfigured to support the second-shaft third supported portion.
 3. Theimage processing device of claim 1, wherein the first-shaft thirdsupporting portion comprises a resin.
 4. The image processing device ofclaim 1, wherein the first shaft comprises a metal.
 5. The imageprocessing device of claim 1, wherein at least one of the first-shaftfirst supported portion and the first-shaft second supported portion ispositioned at an end portion of the first shaft.
 6. The image processingdevice of claim 1, wherein the sensor is an image sensor.